Hazardous environments such as nuclear power plants, chemical processing plants, fuel storage tanks, and the like, require extensive safety precautions, including regular safety checks of systems and components to ensure they will function properly when needed. For example, scram solenoid pilot valves (SSPV) of the type used for emergency shutdown of a boiling water reactor in a nuclear power plant need to be checked on a regular basis to ensure they remain operational. While a number of backup safety measures are usually designed into such hazardous environments to avoid catastrophic failure should one or more of the solenoid valves stop working, it is nevertheless imperative to be able to detect when the valve has malfunctioned.
Prior attempts to detect when a solenoid valve has malfunctioned have included manually checking the solenoid coil, thermally scanning the solenoid coil, and connecting an LED or other status indicator light to the solenoid coil. However, manual checking in a hazardous environment like a nuclear power plant requires plant personnel to be exposed to potentially dangerous levels of radiation. And using thermal scanners may be less reliable for sensing individual solenoid coils when multiple valves are clustered together. LEDs and status indicator lights have been incorporated directly into the solenoid coil, but the lights have decreased life spans due to the coils being continuously energized in most applications. Once burned out, such LEDs and status indicator lights are extremely difficult to remove and replace in the field, often requiring substitution of the entire solenoid valve.
Accordingly, a need exists for a solenoid coil with an operational status indicator that may be quickly and conveniently replaced in the field.